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[texts]String Theory - J. L. F. Barbon
This is a rendering of a review talk on the state of String Theory, given at the EPS-2003 Conference, intended for a wide audience of experimental and theoretical physicists. It emphasizes general ideas rather than technical aspects.
Downloads: 53 4.00 out of 5 stars4.00 out of 5 stars4.00 out of 5 stars4.00 out of 5 stars(1 review)
[texts]Causal set as a discretized phase spacetime - Roman Sverdlov
The first goal of this paper is to show that discreteness, locality, and relativistic covariance can peacefully coexist if the ordinary spacetime (OST) is replaced with phase spacetime (PST) as a geometric background of a Poisson process, where PST is a spacetime generalization of a notion of phase space (this is a 7-dimensional version of the 8-dimensional structure proposed by Caianiello). Furthermore, Caianiello's idea of finite acceleration is implemented...
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[texts]Chronon corrections to the Dirac equation - Andrei A. Galiautdinov
The Dirac equation is not semisimple. We therefore regard it as a contraction of a simpler decontracted theory. The decontracted theory is necessarily purely algebraic and non-local. In one simple model the algebra is a Clifford algebra with 6N generators. The quantum imaginary $\hbar i$ is the contraction of a dynamical variable whose back-reaction provides the Dirac mass. The simplified Dirac equation is exactly Lorentz invariant but its symmetry group is SO(3,3), a decontraction of the Poinca...
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[texts]CP violation in top pair production at an e^+e^- collider - Darwin Chang
We investigate a possible CP violating effect in $e^+e^-$ annihilation into $t\bar t$ top quark pairs. As an illustrative example, we assume the source of the CP nonconservation is in the Yukawa couplings of a neutral Higgs boson which contain both scalar and pseudoscalar pieces. One of the interesting observable effects is the difference in production rates between the two CP conjugate polarized $t\bar t$ states.
Downloads: 2
[texts]Motivic Milnor fiber of cyclic L-infinity algebras - Yunfeng Jiang
We define motivic Milnor fiber of cyclic $L_\infty$-algebras of dimension three using the method of Denef and Loeser of motivic integration. It is proved by Nicaise and Sebag that the topological Euler characteristic of the motivic Milnor fiber is equal to the Euler characteristic of the \'{e}tale cohomology of the analytic Milnor fiber. We prove that the value of Behrend function on the germ moduli space determined by $L$ is equal to the Euler characteristic of the analytic Milnor fiber...
Downloads: 2
[texts]Missing Power vs low-l Alignments in the Cosmic Microwave Background: No Correlation in the Standard Cosmological Model - Devdeep Sarkar
On large angular scales (greater than about 60 degrees), the two-point angular correlation function of the temperature of the cosmic microwave background (CMB), as measured (outside of the plane of the Galaxy) by the Wilkinson Microwave Anisotropy Probe, shows significantly lower large-angle correlations than expected from the standard inflationary cosmological model. Furthermore, when derived from the full CMB sky, the two lowest cosmologically interesting multipoles, the quadrupole (l=2) and t...
Downloads: 2
[texts]Pitfalls on the determination of the universality class of radial clusters - S. C. Ferreira Jr.
The self-affinity of growing systems with radial symmetry, from tumors to grain-grain displacement, has devoted increasing interest in the last decade. In this work, we analyzed features about the interface scaling of these clusters through large scale simulations (up to $3\times 10^7$ particles) of two-dimensional growth processes with special emphasis on the off-lattice Eden model. The central objective is to discuss an important pitfall associated to the evaluation of the growth exponent $\be...
Downloads: 3
[texts]Impact of heterogenous prior beliefs and disclosed insider trades - Fuzhou Gong
In this paper, we present a multi-period trading model by assuming that traders face not only asymmetric information but also heterogenous prior beliefs, under the requirement that the insider publicly disclose his stock trades after the fact. We show that there is an equilibrium in which the irrational insider camouflages his trades with a noise component so that his private information is revealed slowly and linearly whenever he is overconfident or underconfident...
Downloads: 4
[texts]Causal Relativistic Fluid Dynamics - Xinzhong Chen
We derive causal relativistic fluid dynamical equations from the relaxation model of kinetic theory as in a procedure previously applied in the case of non-relativistic rarefied gases. By treating space and time on an equal footing and avoiding the iterative steps of the conventional Chapman-Enskog --- CE---method, we are able to derive causal equations in the first order of the expansion in terms of the mean flight time of the particles...
Downloads: 3
[texts]Parametric Autoresonance in Faraday waves - Michael Assaf
We develop a theory of parametric excitation of weakly nonlinear standing gravity waves in a tank, which is under vertical vibrations with a slowly time-dependent ("chirped") vibration frequency. We show that, by using a negative chirp, one can excite a steadily growing wave via parametric autoresonance. The method of averaging is employed to derive the governing equations for the primary mode. These equations are solved analytically and numerically, for typical initial conditions, for both invi...
Downloads: 3
[texts]The quantum entanglement contained in density matrices - Yong Zhou
We point out that density matrices can only be used to describe quantum states, so the entanglement contained in a density matrix is just quantum entanglement. This means a bipartite state described by a density matrix contains quantum entanglement, unless the density matrix has the form $\rho_{AB}=\rho_A\otimes \rho_B$.
Downloads: 1
[texts]Cosmological Evolution of Global Monopoles - Masahide Yamaguchi
We investigate the cosmological evolution of global monopoles in the radiation dominated (RD) and matter dominated (MD) universes by numerically solving field equations of scalar fields. It is shown that the global monopole network relaxes into the scaling regime, unlike the gauge monopole network. The number density of global monopoles is given by $n(t) \simeq (0.43\pm0.07) / t^{3}$ during the RD era and $n(t) \simeq (0.25\pm0.05) / t^{3}$ during the MD era...
Downloads: 1
[texts]Phases of Supersymmetric D-branes on Kaehler Manifolds and the McKay correspondence - P. Mayr
We study the topological zero mode sector of type II strings on a K\"ahler manifold $X$ in the presence of boundaries. We construct two finite bases, in a sense bosonic and fermionic, that generate the topological sector of the Hilbert space with boundaries. The fermionic basis localizes on compact submanifolds in $X$. A variation of the FI terms interpolates between the description of these ground states in terms of the ring of chiral fields at the boundary at small volume and helices of except...
[texts]arxiv-math0503059
[texts]Chiral symmetry and spectral properties of the Dirac operator in G2 Yang-Mills Theory - Julia Danzer
We study spontaneous chiral symmetry breaking and the spectral properties of the staggered lattice Dirac operator using quenched gauge configurations for the exceptional group G2, which has a trivial center. In particular we study the system below and above the finite temperature transition and use the temporal boundary conditions of the fermions to probe the system. We evaluate several observables: The spectral density at the origin, the spectral gap, the chiral condensate and the recently prop...
Downloads: 2
[texts]Physical Conditions in Obscuring Tori and Molecular Accretion Disks, and Are They Really the Same Thing? - Philip R. Maloney
The nature of the obscuring material in active galactic nuclei is still uncertain. Although some sources, such as Cygnus A, show evidence for a geometrically thick ``torus'' as originally suggested, recent work on the radiation-driven warping instability discovered by Pringle suggests that obscuration by thin, warped disks may play a crucial role in AGN.
[texts]Final-state interactions and superscaling in the semi-relativistic approach to quasielastic electron and neutrino scattering - J. E. Amaro
The semi-relativistic approach to electron and neutrino quasielastic scattering from nuclei is extended to include final-state interactions. Starting with the usual non-relativistic continuum shell model, the problem is relativized by using the semi-relativistic expansion of the current in powers of the initial nucleon momentum and relativistic kinematics. Two different approaches are considered for the final-state interactions: the Smith-Wambach 2p-2h damping model and the Dirac-equation-based ...
Downloads: 1
[texts]Construction of Near-Optimum Burst Erasure Correcting Low-Density Parity-Check Codes - E. Paolini
In this paper, a simple, general-purpose and effective tool for the design of low-density parity-check (LDPC) codes for iterative correction of bursts of erasures is presented. The design method consists in starting from the parity-check matrix of an LDPC code and developing an optimized parity-check matrix, with the same performance on the memory-less erasure channel, and suitable also for the iterative correction of single bursts of erasures...
Downloads: 2
[texts]Momentum deficit in quantum glasses - A. F. Andreev
Using the concept of tunneling two level systems we explain the reduction of rotational inertia of disordered solid 4He observed in the torsional oscillator experiments. The key point is a peculiar quantum phenomenon of momentum deficit for two level systems in moving solids. We show that an unusual state which is essentially different from both normal and superfluid solid states can be realized in quantum glasses...
Downloads: 1
[texts]Sufficiency Criterion for the Validity of the Adiabatic Approximation - D M Tong
We examine the quantitative condition which has been widely used as a criterion for the adiabatic approximation but was recently found insufficient. Our results indicate that the usual quantitative condition is sufficient for a special class of quantum mechanical systems. For general systems, it may not be sufficient, but it along with additional conditions is sufficient. The usual quantitative condition and the additional conditions constitute a general criterion for the validity of the adiabat...
[texts]Vertex Operators are Not Closeable - Wolfram Boenkost
We prove the uncloseability of the free vertex operators used in conformal field theory for the BRST--construction of primary fields. Our proof includes minimal models as well as WZNW--models.
Downloads: 2
[texts]Formation of Bulges - Joseph Silk
Bulges, often identified with the spheroidal component of a galaxy, have a complex pedigree. Massive bulges are generally red and old, but lower mass bulges have broader dispersions in color that may be correlated with disk colors. This suggests different formation scenarios. I will review possible formation sequences for bulges, describe the various signatures that distinguish these scenarios, and discuss implications for the high redshift universe.
[texts]A new gap phenomenon for proper holomorphic mappings from B^n into B^N - Xiaojun Huang
In this paper (Math. Res. Lett. 13 (2006). No 4, 509-523), the authors established a pseudo-normal form for proper holomoprhic mappings between balls in complex spaces with degenerate rank. This then was used to give a complete characterization for all proper holomorphic maps with geometric rank one, which, in particular, includes the following as an immediate application: Theorem: Any rational holomorphic map from B^n into B^N with $4\le n\le N\le 3n-4$ is equivalent to the D'Angelo map $$F_{\t...
[texts]Cosmic Rays and Radiative Instabilities - T. W. Hartquist
In the absence of magnetic fields and cosmic rays, radiative cooling laws with a range of dependences on temperature affect the stability of interstellar gas. For about four and a half decades, astrophysicists have recognised the importance of the thermal instablity for the formation of clouds in the interstellar medium. Even in the past several years, many papers have concerned the role of the thermal instability in the production of molecular clouds...
Downloads: 2
[texts]Ant foraging and minimal paths in simple graphs - M. Vela-Pérez
Ants are known to be able to find paths of minimal length between the nest and food sources. The deposit of pheromones while they search for food and their chemotactical response to them has been proposed as a crucial element in the mechanism for finding minimal paths. We investigate both individual and collective behavior of ants in some simple networks representing basic mazes. The character of the graphs considered is such that it allows a fully rigorous mathematical treatment via analysis of...
Downloads: 2
[texts]Photoluminescence spectrum of an interacting two-dimensional electron gas at ν=1 - R. L. Doretto
We report on the theoretical photoluminescence spectrum of the interacting two-dimensional electron gas at filling factor one (\nu=1). We considered a model similar to the one adopted to study the X-ray spectra of metals and solved it analytically using the bosonization method previously developed for the two-dimensional electron gas at \nu=1. We calculated the emission spectra of the right and the left circularly polarized radiations for the situations where the distance between the two-dimensi...
Downloads: 2
[texts]Total reaction cross sections for neutron-nucleus scattering - K. Amos
Neutron total reaction cross sections at 45, 50, 55, 60, 65, and 75 MeV from nuclei 12C, 28Si, 56Fe, 90Zr, and 208Pb have been measured and are compared with (microscopic) optical model predictions. The optical potentials were obtained in coordinate space by full folding effective nucleon-nucleon interactions with realistic nuclear ground state density matrices. Good to excellent agreement is found.
Downloads: 1
[texts]Unpolarized and polarized quark distributions in the large-Nc limit - D. I. Diakonov
The isosinglet unpolarized and isovector polarized twist-2 quark distributions of the nucleon at low normalization point are calculated in the large-Nc limit. The nucleon is described as a soliton of the effective chiral theory. We derive the expressions for the distribution functions in the large-Nc limit starting from their definition as numbers of partons carrying momentum fraction x in the infinite momentum frame...
[texts]Generalized Stark formulae over function fields - Ki-Seng Tan
We establish formulae of Stark type for the Stickelberger elements in the function field setting. Our result generalizes a work of Hayes and a conjecture of Gross. It is used to deduce a $p$-adic version of Rubin-Stark Conjecture and Burns Conjecture.
Downloads: 2
[texts]On the ultra high energy cosmic rays and the origin of the cosmic microwave background radiation - C. E. Navia
Some inconsistencies to the assumption of a cosmological origin of the cosmic microwave background CMB, such as the absence of gravitational lensing in the WMAP data, open the doors to some speculations such as a local origin to the CMB. We argue here that this assumption agrees with the absence of the GZK cutoff (at least according to AGASA data) in the energy spectrum of the cosmic ray due to the cosmic interaction with the CMB at $6\times 10^{19} eV$ or above...
Downloads: 1
[texts]Decompactification and the g-theorem - Shyamoli Chaudhuri
The paper is being withdrawn. A new submission will follow.
Downloads: 1
[texts]Vapor bubbles 'SUMO' - Ryota Hosoya
We carry out a series of experiments with a special interest on growing and condensing processes of vapor bubble(s) injected into a subcooled pool. We examine effects of the degree of subcooling of the bulk in the pool and injection rate of the vapor into the pool. We pay their special attention to (i) abrupt collapse of the injected vapor bubble to form micrometer-scale bubbles, and (ii) interaction of adjacent vapor bubbles laterally injected to the pool through the orifices...
[texts]Froissart Bound from Gluon Saturation - E. Ferreiro
We demonstrate that the dipole-hadron cross-section computed from the non-linear evolution equation for the Colour Glass Condensate saturates the Froissart bound in the case of a fixed coupling and for a small dipole (Q^2 >> Lambda_{QCD}^2). That is, the cross-section increases as the logarithm squared of the energy, with a proportionality coefficient involving the pion mass and the BFKL intercept (alpha_s N_c/pi)4 ln 2...
[texts]Sign reversal of ac Josephson current in a ferromagnetic Josephson junction - S. Hikino
The ac Josephson effect in a ferromagnetic Josephson junction, which is composed of two superconductors separated by a ferromagnetic metal (FM), is studied by a tunneling Hamiltonian and Green's function method. We obtain two types of superconducting phase dependent current, i.e., Josephson current and quasiparticle-pair-interference current (QPIC). These currents change their signs with thickness of the FM layer due to the 0-$\pi$ transition characteristic to the ferromagnetic Josephson junctio...
Downloads: 1
[texts]Upper critical field, penetration depth, and depinning frequency of the novel high-temperature superconductor LaFeAsO$_{0.9}$F$_{0.1}$ studied by microwave surface impedance - A. Narduzzo
Temperature and magnetic field dependent measurements of the microwave surface impedance of superconducting LaFeAsO$_{0.9}$F$_{0.1}$ (\Tc $\approx$ 26K) reveal a very large upper critical field ($B_{\rm c2} \approx 56$T) and a large value of the depinning frequency ($f_{0}\approx 6$GHz); together with an upper limit for the effective London penetration depth, $\lambda_{\rm eff} \le 200 \rm nm$, our results indicate a strong similarity between this system and the high-$T_{\rm c}$ superconducting ...
[texts]Comment on ``Dynamic Scaling in the Spatial Distribution of Persistent Sites'' - E. Ben-Naim
In a recent paper (cond-mat/9901130), the spatial distribution of unvisited sites in the one-dimensional single-species annihilation process was investigated. It was claimed that this distribution is characterized by a new length scale, and that the corresponding dynamical exponent depends upon the initial concentration. We show numerically that this assertion is erroneous. Regardless of the initial concentration, this spatial distribution is characterized by the diffusive length scale.
Downloads: 2
[texts]Theory of Thermodynamic Stresses in Colloidal Dispersions at the Glass Transition - D. Hajnal
We discuss the nonlinear rheology of dense colloidal dispersions at the glass transition. A first principles approach starting with interacting Brownian particles in given arbitrary homogeneous (incompressible) flow neglecting hydrodynamic interactions is sketched. It e.g. explains steady state flow curves for finite shear rates measured in dense suspensions of thermosensitive core-shell particles consisting of a polystyrene core and a crosslinked poly(N-isopropylacrylamide)(PNIPAM) shell...
Downloads: 2
[texts]On the completeness of a system of coherent states - A. M. Perelomov
Completeness is proved for some subsystems of a system of coherent states. The linear dependence of states is investigated for the von Neumann type subsystems. A detailed study is made of the case when a regular lattice on the complex $\alpha$ plane with cell area S=$\pi$ corresponds to the states of the system. It is shown that in this case there exists only one linear relationship between the coherent states...
[texts]Neon Fine-Structure Line Emission By X-ray Irradiated Protoplanetary Disks - Alfred E. Glassgold
Using a thermal-chemical model for the generic T-Tauri disk of D'Alessio et al. (1999), we estimate the strength of the fine-structure emission lines of NeII and NeIII at 12.81 and 15.55 microns that arise from the warm atmosphere of the disk exposed to hard stellar X-rays. The Ne ions are produced by the absorption of keV X-rays from the K shell of neutral Ne, followed by the Auger ejection of several additional electrons...
Downloads: 5
[texts]Ultra-high energy cosmic rays from a finite number of point sources - M. Kachelriess
We have calculated the probability that the clustering of arrival directions of ultra-high energy cosmic rays (UHECRs) is consistent with a finite number of uniformly distributed proton sources. The case of a continuous source distribution is reached only for an unrealisticly high source density, $n_s\gg 10^{-2}/Mpc^3$. Even for densities as large as $n_s=10^{-3}/Mpc^3$, less than half of the observed cluster are on average by chance...
[texts]Photoassociation adiabatic passage of ultracold Rb atoms to form ultracold Rb_2 molecules - Evgeny A. Shapiro
We theoretically explore photoassociation by Adiabatic Passage of two colliding cold ^{85}Rb atoms in an atomic trap to form an ultracold Rb_2 molecule. We consider the incoherent thermal nature of the scattering process in a trap and show that coherent manipulations of the atomic ensemble, such as adiabatic passage, are feasible if performed within the coherence time window dictated by the temperature, which is relatively long for cold atoms...
[texts]Reply to "Comment on Universal Decoherence in Solids" - Eugene M. Chudnovsky
The Comment of Openov (PRL 93, 158901 (2004)) on my Physical Review Letter (PRL 92, 120405 (2004)) does not affect the universality of the decoherence mechanism described in the Letter.
Downloads: 1
[texts]Origin of the hysteresis in bilayer 2D systems in the quantum Hall regime - L. H. Ho
The hysteresis observed in the magnetoresistance of bilayer 2D systems in the quantum Hall regime is generally attributed to the long time constant for charge transfer between the 2D systems due to the very low conductivity of the quantum Hall bulk states. We report electrometry measurements of a bilayer 2D system that demonstrate that the hysteresis is instead due to non-equilibrium induced current...
[texts]Galactic electrons and positrons at the Earth:new estimate of the primary and secondary fluxes - T. Delahaye
We analyse predictions of the CR lepton fluxes at the Earth of both secondary and primary origins, evaluate the theoretical uncertainties, and determine their level of consistency with respect to the available data. For propagation, we use a relativistic treatment of the energy losses for which we provide useful parameterizations. We compute the secondary components by improving on the method that we derived earlier for positrons...
Downloads: 3
[texts]Singularities of quadratic differentials and extremal Teichmüller mappings defined by Dehn twists - Chaohui Zhang
Let $S$ be a Riemann surface of type $(p,n)$ with $3p-3+n>0$. Let $\omega$ be a pseudo-Anosov map of $S$ that is obtained from Dehn twists along two families $\{A,B\}$ of simple closed geodesics that fill $S$. Then $\omega$ can be realized as an extremal Teichm\"{u}ller mapping on a surface of type $(p,n)$ which is also denoted by $S$. Let $\phi$ be the corresponding holomorphic quadratic differential on $S$...
Downloads: 2
[texts]Application of the operator product expansion to the short distance behavior of nuclear potentials - Sinya Aoki
We investigate the short distance behavior of nucleon-nucleon (NN) potentials defined through Bethe-Salpeter wave functions, by perturbatively calculating anomalous dimensions of 6-quark operators in QCD. Thanks to the asymptotic freedom of QCD, 1-loop computations give certain exact results for the potentials in the zero distance limit. In particular the functional form of the S-state central NN potential at short distance $r$ is predicted to be a little weaker than $r^{-2}$...
Downloads: 2
[texts]Localized Random Lasing Modes and a New Path for Observing Localization - Xunya Jiang
We demonstrate that a knowledge of the density-of-states and the eigenstates of a random system without gain, in conjunction with the frequency profile of the gain, can accurately predict the mode that will lase first. Its critical pumping rate can be also obtained. It is found that the shape of the wavefunction of the random system remains unchanged as gain is introduced. These results were obtained by the time-independent transfer matrix method and finite-difference-time-domain (FDTD) methods...
Downloads: 2
[texts]Hydrodynamical simulations of the jet in the symbiotic star MWC 560. II. Simulations beyond density balance - Matthias Stute
(Abridged) In the first paper of this series, we presented hydrodynamical simulations with radiative cooling of jet models with parameters representative of the symbiotic system MWC 560. These were jet simulations of a pulsed, initially underdense jet in a high-density ambient medium. They were stopped when the jet reached a length of 50 AU. There, however, a transition of the initially underdense jet towards an overdense jet should occur, which should result in changed kinematics...
Downloads: 3
[texts]Systematic errors in the correlation method for Johnson noise thermometry: residual correlations due to amplifiers - Luca Callegaro
Johnson noise thermometers (JNT) measure the equilibrium electrical noise, proportional to thermodynamic temperature, of a sensing resistor. In the correlation method, the same resistor is connected to two amplifiers and a correlation of their outputs is performed, in order to reject amplifiers' noise. Such rejection is not perfect: the residual correlation gives a systematic error in the JNT reading...
[texts]Solution of the Dirichlet boundary value problem for the Sine-Gordon equation - J. Leon
The sine-Gordon equation in light cone coordinates is solved when Dirichlet conditions on the L-shape boundaries of the strip [0,T]X[0,infinity) are prescribed in a class of functions that vanish (mod 2 pi) for large x at initial time. The method is based on the inverse spectral transform (IST) for the Schroedinger spectral problem on the semi-line solved as a Hilbert boundary value problem. Contrarily to what occurs when using the Zakharov-Shabat eigenvalue problem, the spectral transform is re...
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